Ultrasonic transducers have been used for a long time in numerous variants for measuring flow velocities or fill levels. A significant, often reoccurring problem in the use of ultrasonic transducers is the undesired interaction between an ultrasonic transducer element for producing and/or detecting ultrasonic signals and a measuring apparatus, which interaction results from the contact produced via the installation of the ultrasonic transducer into the measuring apparatus. The interaction leads to transfer of oscillations of the measuring apparatus to the ultrasonic transducer element, which superimpose on the measurement signal, such that the registering of measured values becomes difficult. The oscillations of the measuring apparatus can, in such case, come from a remote location, or also from post-pulse oscillations produced by the ultrasonic transducer element or from additional ultrasonic transducers. Post-pulse oscillations arise from sound decay or reverberation of the ultrasonic transducer element after producing an ultrasonic signal radiated into a medium.
To solve this problem, for example, a housing of the ultrasonic transducer containing the ultrasonic transducer element is insulated acoustically from a meter body by means of a cladding; see US2015308870A1. This solution has the disadvantage that, because of not being able to produce a perfect acoustic insulation, all eigenoscillations of the housing can be excited and therewith the ultrasonic transducer element can be disturbed.
Another approach for avoiding the problem of interaction between the ultrasonic transducer element and the measuring apparatus is disclosed in the document, EP1340964A1. An ultrasonic transducer arrangement with an ultrasonic transducer element and a bending plate radiating ultrasonic waves is held by a filter, wherein the filter provides for an acoustic insulation of an ultrasonic transducer element from a housing. The filter, in such case, contacts the bending plate on its outer edge and thus strongly influences the oscillation characteristics of the bending plate. Moreover, the contact of an acoustic filter with a strongly oscillating bending plate is disadvantageous for an acoustic decoupling of the ultrasonic transducer from the housing.